|Opriessnig, T - IOWA STATE UNIVERSITY|
|Fenaux, M - VIRGINIA POLYTECHNIC|
|Yu, S - IOWA STATE UNIVERSITY|
|Evans, R - IOWA STATE UNIVERSITY|
|Cavanaugh, D - IOWA STATE UNIVERSITY|
|Gallup, J - IOWA STATE UNIVERSITY|
|Pallares, F - UNIVERSIDAD DE MURCIA|
|Thacker, E - IOWA STATE UNIVERSITY|
|Meng, X - VIRGINIA POLYTECHNIC|
|Halbur, P - IOWA STATE UNIVERSITY|
Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 2004
Publication Date: March 5, 2004
Citation: Opriessnig, T., Fenaux, M., Yu, S., Evans, R.B., Cavanaugh, D., Gallup, J.M., Pallares, F.J., Thacker, E.L., Lager, K.M., Meng, X.J., Halbur, P.G. 2004. Effect of porcine parvovirus vaccination on the development of PMWS in segregated early weaned pigs coinfected with type 2 porcine circovirus and porcine parvovirus. Veterinary Microbiology. 98(3-4):209-220. Interpretive Summary: Postweaning multisystemic wasting syndrome (PMWS) is a disease of swine first reported in the late 1990s. Although the cause of PMWS is not fully understood, it appears that porcine circovirus type 2 (PCV2) plays a major role in this disease. Based on experimental and field observations, PMWS usually occurs in pigs following a mixed infection of PCV2 and some other agent, for example, porcine parvovirus (PPV). Field reports indicate that PPV vaccination will decrease the incidence and severity of PMWS in pigs. Objectives of this study were to determine if coinfection of pigs with PCV2 and PPV induced an increase in the incidence of PMWS compared to singular PCV2 infection, and to determine if vaccination against PPV would reduce the incidence of PMWS associated with PCV2/PPV coinfection in pigs. Pigs were randomly assigned to one of five groups: group 1 was negative controls, group 2 was inoculated with PCV2, group 3 was inoculated with PPV, and pigs in group 4 and 5 were inoculated with both PCV2 and PPV. At 24 and 10 days prior to inoculation, pigs in groups 1, 2, 3, and 5 were vaccinated with a killed parvovirus vaccine. The majority of the singular PCV2-infected pigs had mild disease consistent with PMWS field cases. The PCV2/PPV coinfected pigs (groups 4 and 5) had more severe disease than the singular PCV2-infected pigs. One pig in each of the coinfected groups developed severe disease (fever, respiratory disease, jaundice, weight loss) consistent with PMWS. Vaccination was able to prevent PPV-viremia but it was not able to prevent clinical PMWS in PCV2/PPV-coinfected pigs. Additional studies would be needed to confirm the field observations that PPV vaccination can reduce the incidence of PMWS.
Technical Abstract: Objectives of this study were to determine if coinfection of segregated early weaned (SEW) pigs with porcine circovirus type 2 (PCV2) and porcine parvovirus (PPV) induces an increase in the incidence of postweaning multisystemic wasting syndrome (PMWS) compared to singular PCV2 infection, and to determine if vaccination against PPV protects pigs against PMWS associated with PCV2/PPV coinfection in SEW pigs. Seventy, three-week-old, SEW pigs were randomly assigned to one of five groups: group 1 pigs (n=14) were sham-inoculated, the negative controls; group 2 pigs (n=14) were inoculated with PCV2; group 3 pigs (n=12) were inoculated with PPV; and pigs in group 4 (n=16) and 5 (n=14) were inoculated with both PCV2 and PPV. At 24 and 10 days prior to inoculation, pigs in groups 1, 2, 3, and 5 were vaccinated with a killed parvovirus vaccine. PCV2/PPV coinfected pigs (groups 4 and 5) had significantly (p<0.05) higher and more persistent fevers than the singular PCV2-infected pigs. One pig in each of the coinfected groups developed clinical disease (fever, respiratory disease, jaundice, weight loss) consistent with PMWS. The majority of pigs in both the singular PCV2-infected and the PCV2/PPV dual infected groups had enlarged lymph nodes and lymphoid depletion consistent with that observed in field cases of PMWS; however, the lymphoid depletion was significantly (p<0.05) more severe in the dually-infected pigs at 42 days post inoculation (DPI). The mean length of PCV2-viremia was 4.9±0.63, 4.0±0.69, and 6.0±0.00 weeks in group 2, 4, and 5 pigs respectively. In comparison to group 4 (unvaccinated, coinfected) pigs, group 5 (vaccinated, coinfected) pigs remained viremic significantly (p<0.05) longer and had higher copy numbers of genomic PCV2 DNA in sera at 28, 35, and 42 DPI. PPV-viremia was detected only in the unvaccinated group 4 pigs with a mean length of viremia of 0.75±0.11 weeks. Vaccination was able to prevent PPV-viremia but was not able to prevent clinical PMWS or reduce the severity of lymphoid depletion in PCV2/PPV-coinfected pigs. Evidence of increased incidence of clinical PMWS due to vaccination was not observed in this model.